The application of lipases for hydrolyzing and/or modifying fats has been recognized for many years. More recently, lipolytic enzymes have been found to be suitable for industrial use. For example, lypolytic enzymes have been found to be useful for improving the milk flavor in certain dairy products. Lipases have also been used by the pharmaceutical industry for inclusion in digestive aids. Other industrial uses for lipolytic enzymes include interesterification of oils and fats, esterification of fatty acids, digestive aids in animal feeds and additives to washing and cleaning products. As a result of the increased acceptance of these applications, the demand for lipases is expected to grow rapidly in the future.
Lipases from animal, plant and microbial origin have been isolated and their properties have been studied extensively. These enzymes catalyze the hydrolysis of water soluble carboxylic acid esters (triglycerides) while the hydrolysis of water soluble carboxylic acid esters by lipase is very slow. The ability to catalyze the hydrolysis of insoluble long chain fatty acid esters thus distinguishes lipases from other esterases which catalyze hydrolysis of soluble esters in preference to insoluble esters.
Microbial lipase is conveniently produced by fermentation with microorganisms such as Aspergillus niger, Candida cylindracae, Mucor miehei, M. javanicus, Rhizopus delemar, R. arrhizus and Pseudomonas fluorescens which will secrete this enzyme through its cell wall. However, with many microorganisms capable of producing extracellular lipase, a substantial portion of the enzyme apparently remains attached to the cell wall. Sigima and Isobe, 1975, 1976 (Chemical and Pharmaceutical Bulletin, 23, p. 68, 1226 and 24, p. 72) have reported that microbial lipases show exceptionally high surface activity at air water and heptane water interfaces when compared to other groups of proteins. This high surface activity results in a strong adsorption of the lipase onto hydrophobic surfaces of the cell wall. This phenomenon has been observed in conjunction with microbial lipase secreted by a fungus of the species Mucor miehei.
In the case of fermentation of the fungal species Mucor miehei, more than 99% of the extracellular lipase produced is bound to the fungal mycelium while extracellular microbial rennet also produced by this organism is distributed freely in the fermentation broth. In U.S. Pat. No. 3,899,395 there is disclosed a method for recoverying microbial lipase from the fermentation growth product of a Mucor species which involves adsorbing the fermentation growth product with a material selected from diatomaceous earth or clay at a pH of from 4 to 6 and then eluting the lipolytic enzyme by adjusting the pH to a range of from 9 to 11.